Modified anisotropic diffusion for image smoothing and enhancement
Zhong Tang, Ross Whitaker · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2001
This paper discusses an improved nonlinear filtering approach based on anisotropic diffusion technique. This modified anisotropic diffusion method smooths along curve directions, i.e. the directions of level sets. The upwind scheme for level set is used to solve the diffusion equation. Compared with the conventional anisotropic diffusion, which depends only on the local gradient of intensities of the processed image, this modified scheme overcomes the defect of indefinite edge enhancement associated with Perona-Malik model while depressing noises in a better performance. Moreover, a multi-scale diffusion technique is applied to limit blurring by the presence of edges as measured at the scale of interest, so that accurate information about boundaries of objects could be preserved and small details that fall below the scale of interest be removed. Then an extension into vector-valued diffusion is also presented in this paper, which is capable of smoothing small objects while maintaining boundaries information in vector-valued images. Experiments on gray-scale and color images demonstrate the efficacy of this method in image smoothing as well as image enhancement.